1. Field of the Invention
The present invention relates generally to computer-implemented methods and automated systems for visually collecting geometrical, analytical measurements from deformable material specimens and determining mechanical properties and, in particular, to methods and systems for determining mechanical properties of tissue samples and other biomaterial.
2. Description of Related Art
Mechanical test machines are used routinely in engineering applications to determine material properties. These machines typically provide displacement data by using a linear variable differential transformer (LVDT) and force data or load data by means of a load cell. In order to convert the data generated or output by a load cell and linear variable differential transducer (LVDT) into values that describe the mechanical properties of the specimen or material being tested, the geometry of physical dimensions of the specimen must be determined. However, soft tissue samples are easily deformable and pose a particular challenge in geometrical or physical measurement.
Many prior art measurement processes rely on xe2x80x9ccontact methodsxe2x80x9d in which the process itself can affect the specimen dimensions. A non-contact method is needed for accurate measurement of this type of specimen. Further, soft tissues are highly extensible and viscoelastic. In order to track their significant dimensional changes in response to external loading forces, a real-time measurement method is required. Also, unlike harder, tougher biological specimens such as bone, cartilege, or inorganic samples such as glasses, plastics or metals that can be consistently machined to specific dimensions, soft tissue specimens and other biomaterial tend to contain inherent non-uniformities and are difficult to machine. The ability to concurrently collect dimensional measurements at multiple points on the specimen without influencing the dimensions being measured provides a real benefit in these and other applications of this nature.
In the article entitled xe2x80x9cA New Method for Determining Cross-Sectional Shape and Area of Soft Tissues,xe2x80x9d by Lee, T. Q. and Woo, S. L-Y., published in the Journal of Biomechanical Engineering at 110:110-114 (1988), an assessment of the cross-sectional area of soft tissues using an image reconstruction technique is disclosed. This image reconstruction technique is based on measurements from collimated laser beams, and using this procedure, the actual shape of the specimen cross-section can be determined. However, this method does not provide the ability to measure cross-sectional area at multiple points along the length of the specimen simultaneously. In addition, this method does not allow for real-time measurements while the specimen is installed or loaded in a mechanical test machine. Further, this method does not include any instruction on how to perform property calculations or create specified reports or graphical displays of these properties. Still further, this method does not create a video record of the mechanical test or allow correlation of the data to this video.
Another method is disclosed in xe2x80x9cA New Methodology to Determine the Mechanical Properties of Ligaments at High Strain Rates,xe2x80x9d by Peterson, R. H. and Woo, S. L-Y., published in the Journal of Biomechanical Engineering at 108:365-367 (1986). This method uses a video camera as a non-contact means for gathering straining measurements of soft tissues. In addition, this method discusses studying the strains at any specific area along the ligament substance to detect the variation of strains along the length of the tissue. However, this method does not calculate cross-sectional area and, therefore, cannot produce accurate results for certain mechanical property calculations that require this information. Also, this method does not include any methods or the ability to perform property calculations to create graphical reports and displays of the same. In addition, the data, such as the image data from the video record, is not correlated with the calculated mechanical property data.
xe2x80x9cThe use of a laser micrometer system to determine the cross-sectional shape and area of ligaments: a comparative study with two existing methods,xe2x80x9d by Woo, S. L., Danto, M. I., Ohland, K. J., Lee, T. Q. and Newton P. O., published in the Journal of Biomechanical Engineering at 112(4):426-31 (Nov. 1990) discloses a method of determining cross-sectional shape and area of soft tissues. The system disclosed in this article describes the use of a laser micrometer system to determine the cross-sectional area of ligaments. This system does not use a camera or any image data, instead using a static laser measurement system. While the system does allow for non-contact cross-sectional area measurements, it does not allow for measuring cross-sectional area at multiple points along the length of the specimen simultaneously. In addition, it does not provide real-time measurements while the specimen is installed or loaded in a mechanical test machine. In addition, the system does not include any software or methodology to perform property calculations or create graphical reports or display information. Still further, this system does not create any video record of the mechanical test or allow correlation of data to the video record.
Another method is disclosed in xe2x80x9cA new method for determining cross-sectional shape and area of soft tissue,xe2x80x9d by Lee, T. Q. and Woo, S. L., published in the Journal of Biomechanical Engineering at 110(2): 110-4 (May 1988). As discussed above, this method does allow for the determination of cross-sectional area of soft tissues. This system uses a laser and does not allow for measuring of cross-sectional area at multiple points along the length of the specimen simultaneously. Further, the methodology does not allow for real-time measurements while the specimen is installed or loaded in a mechanical test machine. Further, this method does not include any software or methodology to perform property calculations or create reports or graphical displays of these calculations and, therefore, does not correlate the data obtained from the mechanical test to any video record of the same.
A further method is disclosed in xe2x80x9cA new method of measuring the cross-sectional area of connective tissue structures,xe2x80x9d by Shrive, N. G., Lam, T. C., Damson, E. and Frank, C. B., published in the Journal of Biomechanical Engineering at 110(2): 104-9 (May 1988). This method allows for the measurement of cross-sectional area of connective tissue structures. The method uses an instrument to measure the thickness of the tissue as a function of position along the width of the tissue. This method does not use a camera and does not allow for the measuring of cross-sectional area at multiple points along the length of the specimen simultaneously. The method does not disclose the use of real-time measurements conducted while the specimen is installed or loaded in a mechanical test machine. No methodology or software is disclosed that can perform the property calculations or create reports or graphical displays of these calculations. The method does not create a video record of the mechanical test or allow the correlation of the video to the calculated data. In addition, while this method does claim to be non-destructive, it does not claim to be a non-contact method.
xe2x80x9cA method of in-vitro measurement of the cross-sectional area of soft tissues, using ultrasonography,xe2x80x9d by Noguchi, M., Kitaura T., Ikoma, K. and Kusaka Y., published in the Journal of Orthopedic Science at 7(2): 247-51 (2002) discloses yet another method that determines the cross-sectional area of soft tissues in a non-contact manner. The method uses ultrasonography, and not a camera, and further does not allow for the measurement of cross-sectional area at multiple points along the length of the specimen simultaneously. Further, the method does not allow for real-time measurements while the specimen is installed or loaded in a mechanical test machine. No software or methodology is disclosed to perform property calculations or create reports or graphical displays of these calculations, and no video record of the mechanical test or correlation of the data to this video is taught in this publication.
xe2x80x9cA microcomputer-based vision system for area measurement,xe2x80x9d by Kim, N. H., Wysocki, A. B., Bovik, A. C. and Diller, K. R., published in Computers in Biology and Medicine at 17(3): 173-83 (1987) discloses a microcomputer-based vision system for area measurements. The algorithm disclosed allows the use of images in determining areas and cross-sections of cell and multicellular tissue. These measurements are gained in a non-contact manner and a camera is used. However, this system does not allow for real-time measurements while the specimen is installed or loaded in a mechanical test machine. Further, no software or methodology is described, which would perform property calculations and create reports or graphical displays of these calculations. This system is not designed for use in conjunction with mechanical tests, and therefore does not allow correlation of any data with video. It does not appear that this system can be used for measuring cross-sectional area at multiple points along the length of the specimen simultaneously.
xe2x80x9cA device to measure the cross-sectional area of soft connective tissues,xe2x80x9d by Vanderby, R., Jr., Masters, G. P., Bowers, J. R. and Graf, B. K., published in IEEE Transactions on Biomedical Engineering at 38(10): 1040-2 (Oct. 1991) discloses a device to measure the cross-sectional area of soft connective tissues ex vivo. Displacement transducers are used to output information to a personal computer. This device does not use a camera, but uses displacement transducers and the device does not allow for the measurement of cross-sectional area at multiple points along the length of the specimen simultaneously. Further, the device does not provide real-time measurements while the specimen is installed or loaded in a mechanical test machine. This device does not include any software or methodology to perform property calculations and create reports and/or graphical displays of these calculations. Still further, the device does not create a video record of the mechanical tests or allow correlation of data to this video.
xe2x80x9cMeasurements of cross-sectional area of collagen structures (knee ligaments) by means of an optical method,xe2x80x9d by laconis, F., Steindler, R. and Marinozzi G., published in Journal of Biomechanical Engineering at 20(10):1003-10 (1987) discloses yet another methodology to measure cross-sectional area of collagen structures by using an optical system. This methodology does not allow for the measurement of cross-sectional area at multiple points along the length of the specimen simultaneously. In addition, the system does not permit real-time measurements while the specimen is installed or being loaded in a mechanical test machine and, further, does not include any software or method to perform property calculations or create reports or graphical displays of these calculations. Area calculations are not performed in the context of a mechanical test, and, therefore, no such video record can be correlated to the produced data. This system requires sectioning of the specimen and is therefore destructive and cannot be non-contact in nature.
It is, therefore, an object of the present invention to provide a method and system for measuring the mechanical properties of deformable materials, such as tissue and other such biomaterial. It is another object of the present invention to provide a method and system for measuring mechanical properties of deformable materials that uses an optical system, such as camera devices, and simultaneously measures the cross-sectional area of the specimen at multiple points along the length of the specimen. It is another object of the present invention to provide a method and system for measuring the mechanical properties of deformable materials that uses real-time measurements while the specimen is installed or being subjected to load in a mechanical test machine. It is a still further object of the present invention to provide a method and system for measuring mechanical properties of deformable materials that accurately performs property calculations and creates reports and graphical displays of these calculations to the user. It is yet another object of the present invention to provide a method and system for measuring mechanical properties of deformable materials that creates a video record of the mechanical test and allows the correlation of data and calculations to this video. It is a still further object of the present invention to provide a method and system for measuring mechanical properties of deformable materials that conducts cross-sectional area measurements in a non-contact manner.
Accordingly, we have invented a system for measuring mechanical properties of a deformable material specimen. The system includes a first gripping device for removably securing a first end of the specimen, and a second gripping device for removably securing a second end of the specimen. An image acquisition device is positioned with respect to the specimen and produces image data reflective of a specified area of the specimen. Either the first gripping device or the second gripping device is movable in a first direction and is in communication with the displacement measurement mechanism. This displacement measurement mechanism produces displacement data reflective of the position of the movable gripping device. The system also includes a load measurement mechanism in communication with either the first gripping device or the second gripping device. This load measurement mechanism produces load data reflective of the force experienced by the first gripping device or the second gripping device.
In another aspect of the present invention, a computer-implemented method is disclosed for determining mechanical properties of a deformable material specimen. This method includes the steps of: (a) removably securing a first end of the specimen in a first gripping device; (b) removably securing a second end of the specimen in a second gripping device; (c) obtaining image data reflective of at least one physical dimension of a portion of the specimen in an initial state; (d) applying a load to the specimen by moving either the first gripping device or the second gripping device; (e) measuring the displacement of the moved gripping device therefore producing displacement data; (f) measuring the load placed upon the specimen, thereby producing load data; and (g) calculating a specimen property based at least partially on the image data, the displacement data and the load data.
In a preferred embodiment of the present system, a control mechanism is included and is in communication with the image acquisition device, the displacement measurement mechanism and the load measurement mechanism. This control mechanism receives respective image data, displacement data and load data from the image acquisition device, the displacement measurement mechanism and the load measurement mechanism. The control mechanism is in communication with a visual display device which displays information and data direct to the image data, the displacement data, the load data or any data calculated by the control mechanism.
In another preferred embodiment, the displacement measurement mechanism is a linear variable differential transformer and the load measurement mechanism is a load cell. Further, the image acquisition device is preferably a first camera device and a second camera device, each having a field of vision. The first camera device and the second camera device are positioned at 90 degrees with respect to each other in order to collect specified area information of separate surfaces of the specimen. Further, the first camera device and the second camera device may be connected to an image acquisition control mechanism, which serves to receive, process and transmit information to the control mechanism.
The present invention, both as to its construction and its method of operation, together with the additional objects and advantages thereof, will best be understood from the following description of exemplary embodiments when read in connection with the accompanying drawings.